"Hostility" refers to a set of characteristics that appear to be associated with diminished or dysregulated central serotonergic function, and that are linked, as well, with a number of lifestyle and biological variables associated with coronary heart disease (CHD) risk. For example, hostility has been shown to be associated with increased smoking and alcohol consumption, unhealthy dietary patterns, altered lipid concentrations, alterations in autonomic balance, increase stress-related cardiovascular responsiveness, and increased platelet activation. Accumulating evidence suggests that hostile characteristics are associated with increased risk for CHD events and mortality: These unhealthy behavioral and biological processes may account, in part, for the observed associations between hostility and CHD. Selective serotonin reuptake inhibitors (SSRIs), which increase the efficiency of serotonergic neurotransmission, have been shown to reduce hostile traits in psychiatric samples, and some evidence suggests that they may have similar effects in normal volunteers. There are no published data examining the effects of SSRI interventions on measures on hostility previously linked with CHD risk. Moreover, the potential impact of such interventions on multiple behavioral and biological variables of relevance to CHD has not been systematically explored. This project is a placebo-controlled trial designed to examine the effects of short term (3 month) SSRI treatment on changes in hostility and aggression in normal volunteers, selected for high hostility. We will also examine the effects of this intervention on changes in lifestyle- related behaviors associated with CHD risk, including smoking, alcohol consumption, and unhealthy dietary patterns; and on changes in biological markers of disease risk, including lipids, glucose and insulin, autonomic balance, stress-related cardiovascular responsiveness, and platelet activation. This research is important in 3 ways. First, it will help us to understand some of the CNS correlates of psychological traits relevant to CHD. Second, it will help us to explore some of the common origins of behavior and biological indices of CHD risk.. Second, it will help us explore some of the common origins of the behavioral and biological indices of CHD risk. And third, this research may eventually have implications for the development of new approaches to CHD risk factor intervention.